[mottosso]

I was looking for exactly this about two weeks ago for a 3D editor UI and ended up with Facebook's Yoga library. So far things are running smooth.

I would look closer at this library too, if it wasn't for:

"Clay UI hierarchies are built using C macros"

Yikes :S

[jacobp100]

Yoga is pretty good. Used to have a few bugs that stayed around way too long when it was abandoned for a few years. Development has picked up again though